IBM PS/2 Model 70
| Company type | Product line |
|---|---|
| Industry | Computer hardware |
| Founded | June 1988 |
| Headquarters | Boca Raton, Florida (initial manufacturing) , United States |
Area served | Worldwide |
Key people | Mark Dean (chief engineer) |
| Products | Personal computers (desktop and portable) |
| Parent | IBM |
The Personal System/2 Model 70 386 and Model 70 486 represent IBM's midrange desktop offerings within the Personal System/2 lineup. Debuting in June 1988, the Model 70 386 is equipped with an Intel 386 CPU operating between 16 and 25 MHz and utilizes a 32-bit Micro Channel architecture (MCA) bus. The Model 70 486 followed in December 1989, powered by a i486 processor clocked at 25 MHz, maintaining the same MCA bus architecture. Essentially, the Model 70 486 came with the 486/25 Power Platform—a CPU upgrade card for the Model 70 386 released earlier that year and recognized as the first commercial product featuring the 486 processor. Both models employ the identical chassis design previously used in the IBM PS/2 Model 50 from 1987.
Development and release
Development of both Model 70 versions took place at IBM’s Boca Raton facility in Florida. The initial Model 70 386 was launched on June 2, 1988. Mark Dean, notable for leading projects such as the IBM PS/2 Model 80, the IBM Personal Computer AT, and the Industry Standard Architecture bus, served as chief engineer for this model. Work on the Model 70 commenced in 1986 concurrently with the first PS/2 series. By April 1987, prototypes had been shared with select media and insiders, though the official announcement was postponed until May 1988. During this period, IBM introduced the PS/2 Model 80, their first Intel-based tower PC designed for expandability and initially aimed at multiuser workstations before being repositioned as a server; consequently, the Model 70 assumed the workstation role.
Both versions utilize the same casing and tool-less assembly design introduced with the earlier Model 50 in April 1987. Manufacturing initially took place in Boca Raton alongside other PS/2 units until early 1989, when production was relocated to Raleigh, North Carolina following closure of the Florida plant to focus resources on other product lines. Hard drives were fabricated at IBM Japan’s Fujisawa facility.
The Model 70 encountered several design difficulties upon release. The Model 70 386-A21 suffered from faulty processor complex slots that led to system failures, resulting in a temporary halt in production and subsequent motherboard redesigns in early 1989. Additionally, in June of that year, IBM issued a recall for certain submodels equipped with defective 120-MB hard drives due to oil lubricant leaks traced back to manufacturing defects at Fujisawa. Although no data loss was reported, around 25,000 units were recalled to resolve these problems.
486/25 Power Platform
In June 1989, IBM unveiled the 486/25 Power Platform—an upgrade kit for the Model 70 386-A21 comprising a CPU daughtercard (referred to by IBM as a complex) fitted with a 25-MHz Intel 486 processor. This upgrade replaced the original processor complex running at 25 MHz and enabled performance twice that of typical 33 MHz 386 machines while incorporating an integrated floating-point unit. Notably, the 486/25 Power Platform was the first commercial offering featuring Intel’s new 486 processor, announced two months post Intel’s launch and available from early October that year.
Shortly thereafter, less than a month after its release, a minor calculation flaw was identified in early versions of the 486 chip. Although this bug was infrequently encountered during normal use, IBM suspended shipments until Intel provided a corrected version in December 1989. Around this time, Apricot Computers introduced the VX FT—the world’s first preassembled computer with a built-in 486 processor—in early December; it also employed Micro Channel architecture similar to IBM’s Model 70.
On December 19, 1989, IBM officially launched the PS/2 Model 70 486: their first factory-configured system integrating an onboard 486 CPU. This model closely mirrored the earlier Model 70 386 but featured the preinstalled 486/25 Power Platform along with updated branding. Initial shipments reached corporate customers late that month, with broader volume deliveries scheduled for mid-January 1990.
Specifications
Every variant of the Model 70 series is equipped with three Micro Channel expansion slots: two of these are 32-bit, while one is 16-bit. The 16-bit slot is compatible with certain MCA graphics adapters, including the 8514/A.
Model 70 386
The first generation of the Model 70 386 was introduced in June 1988, featuring two models: the Model 70 386-E61 running at 16 MHz and the Model 70-121 operating at 20 MHz. The E61 came with 1 MB of RAM and a 60-MB ESDI hard disk, whereas the 70-121 doubled both memory and storage capacity. Both models allowed memory expansion up to 16 MB and contained a socket for an optional 387 math coprocessor.
In December 1988, IBM launched the premium Model 70 386-A21, which included a redesigned motherboard. This model utilized a daughtercard housing a 25-MHz Intel 386 CPU, a socket for the 387 coprocessor, and featured 64 KB of SRAM cache controlled by an Intel 82385 chip. It came standard with a 120-MB ESDI hard drive.
September 1989 saw IBM release two budget-friendly options: the Model 70-061, a 20-MHz system with a 60-MB hard disk, and the Model 70-A61, a streamlined version of the A21 also equipped with a 60-MB drive.
Following a two-year break, IBM expanded the Model 70 lineup in December 1991 by introducing four new configurations: the Model 70 386-A81 (25 MHz, 80 MB), A16 (25 MHz, 160 MB), –081 (20 MHz, 80 MB), and –161 (20 MHz, 160 MB). All four shipped with a base memory of 4 MB RAM.
IBM officially discontinued the PS/2 Model 70 386 series in October of 1992.
Model 70 486
The Model 70 486 was unveiled in December 1989 and was available in two versions: the 486-B21 with a 120-MB ESDI hard drive and the 486-B61 equipped with a smaller, 60-MB ESDI drive. Both models featured a 25 MHz Intel 486 processor and were essentially rebranded versions of the Model 70-121 and Model 70–061 but included the preinstalled Power Platform for the 486/25. The production run for the Model 70 486 ended in June of 1991, less than two years after its debut.
Portable model
In May of 1989, IBM introduced the PS/2 Model P70, a portable adaptation of the PS/2 Model 70 386. This model weighed approximately and came with an integrated carrying handle. It was powered by a 20-MHz Intel 386 processor and included 4 MB of RAM alongside an amber-tinted monochrome gas plasma flat-panel display. This release marked IBM’s third attempt to penetrate the US portable PC market following earlier less successful efforts.
Reception
The PS/2 Model 70 386 received favorable evaluations from industry reviewers. Stephen Satchell from InfoWorld regarded the Model 70 386-121 as an excellent value proposition, noting that it outperformed the more expensive PS/2 Model 80 equipped with the same processor. Christopher O'Malley of Personal Computing identified the Model 70 386-A21 as the fastest among competing machines running at 25 MHz from brands like Compaq and Advanced Logic Research but pointed out its limited upgrade potential due to its proprietary ESDI hard drive interface. Several InfoWorld critics recommended this system for technical uses such as CAD/CAM applications but gave it low marks as a file server. Bruce Brown writing for PC Magazine summarized: "IBM's PS/2 Model 70s blend compact design, robust modularity, and substantial power across three premium-priced computers," while acknowledging some constraints in expandability but praising their extensive built-in features.
Submodels
| Model | IBM P/N | CPU | Clock speed (MHz) |
Bus type | Expansion slots |
Drive bays |
FDD | HDD | Default RAM |
Max. RAM |
Graphics adapter | Display | Chassis type | Release date | Remarks |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| 70 386 | 8570-061 | Intel 386 | 20 | MCA, 32-bit | 3 | 3 | single 1.44 MB | 60 MB (ESDI) | 2 MB | 6 MB | VGA | optional | Desktop | Template:Date table sorting | |
| 70 386 | 8570-081 | Intel 386 | 20 | MCA, 32-bit | 3 | 3 | single 1.44 MB | 60 MB (ESDI) | 4 MB | 6 MB | VGA | optional | Desktop | Template:Date table sorting | |
| 70 386 | 8570-121 | Intel 386 | 20 | MCA, 32-bit | 3 | 3 | single 1.44 MB | 120 MB (ESDI) | 2 MB | 6 MB | VGA | optional | Desktop | Template:Date table sorting | |
| 70 386 | "8570-161" | "Intel 386" | "20" | "MCA, 32-bit" | "3" | "3" | "single 1.44 MB" | "160 MB (ESDI)" | "4 MB" | "6 MB" | "VGA" | "optional" | "Desktop" | "1991-06" | |
| "70 386" | "8570-A16" | "Intel 386" | "25" | "MCA, 32-bit" | "3" | "3" | "single 1.44 MB" | "160 MB (ESDI)" | "4 MB" | "6 MB" | "VGA" | "optional" | "Desktop" | "1991-06" | |
| "70 486" | "8570-B21" | "Intel 486" | "25" | "MCA, 32-bit" | "3" | "3" | "single 1.44 MB" | "120 MB (ESDI)" | "2 MB" | "8 MB" | "VGA" | "optional" | "Desktop" | "1989-12" | |
| "70 486" | "8570-B61" | "Intel 486" | "25" | "MCA, 32-bit" | "3" | "3" | "single 1.44 MB" | "60 MB (ESDI)" | "2 MB" | "8 MB" | "VGA" | "optional" | "Desktop" | "1989-12" |